The invention relates to a magnetic drive arrangement comprising at least three magnetically cooperating parts which are movable relative to one another, one part being provided for connection to a drive shaft, one part being provided for connection to an output shaft, and one part being provided as a stationary part, a first and a second part comprising permanent magnets which alternately exhibit north poles and south poles along the circumference, a third part having teeth of a magnetically conductive material for modulating the magnetic fields generated by the permanent magnets.
A magnetic drive arrangement of the type defined in the opening paragraph is known from EP 669 700, to which U.S. Pat. No. 5,633,555 corresponds. In this known drive arrangement the toothed third part is interposed as a central part between the first part and the second part. The individual teeth of this third part are interconnected by portions that must be very thin because otherwise they will short-circuit the magnetic flux generated by the magnet poles of the second part. The portions between the teeth of the third part are highly saturated in operation.
As a result of the requirement that the portions between the teeth of the third part must be thin, the third part can only be manufactured with a limited mechanical stability. This is a substantial drawback, particularly in the case of magnetic drive arrangements which serve to transmit larger torques.